This invention relates to backpack systems for carrying loads without the use of a rigid frame structure, and more particularly to improved systems for bearing loads with less fatigue and without restricting the mobility of the user, such as buoyancy compensated jackets for scuba divers.
The problem of increasing the load carrying capacity of a person has been attacked in various ways through recorded history. Depictions carried down from earlier civilizations have shown that very large burdens have been transported by humans, such as through the use of tump lines extending across the forehead for a load carried on the back, and loads suspended on either side of a person from a beam balanced on the shoulders. Where no road system exists, or where loads have had to be transported across arbitrary terrain, as in military operations, many supports have been devised and used. Until about the end of the first half of the twentieth century, these usually comprised a rigid frame with little or no conformity to the back of the user, and a shoulder strap and belt arrangement that was often unpadded. The center of gravity of the load was well out from the back so that the pull on the shoulder straps was often extremely tiring, and the frame itself was often heavy and added substantially to the base weight. These types of packs were supplemented a number of other types, including those known as "Trapper Nelson" and "A frame" packs. These would typically be lighter but otherwise suffered from most of the same deficiencies although they were widely used.
Shortly after the first half of the twentieth century, however, there was increasing growth in recreational backpacking, and a new market opened up for backpacks of a different type. These were usually more costly, but they enabled users to carry a given load with greater comfort, such as the "Kelty" pack introduced by the A. I. Kelty Company. The frame was made of welded aluminum curved to conform closely to the back of the user, and the pack was removably attachable, and positioned in such a way as to shift the center of gravity of the load both higher and more closely spaced to the back of the individual. The back was supported both by a wide waist belt and by adjustable shoulder pad and strap combinations. Thus the downward press of the load thus tended to be exerted more on the hips of a slightly forwardly leaning hiker. This design was followed by a diverse variety of pack frames, with both external and internal pack arrangements, for comfort and convenience.
While a frame is generally needed for the highest capacity loads, there are a number of situations in which the frame restricts movement or occupies too much space. Therefore, soft packs, without frames or supports, are now widely used to carry moderate loads for recreational hiking, for their capability for storage in aircraft overhead compartments, for cross-country skiers, for climbers and others. Here there is a limited amount of conformity with the backpack, but because it is usually supported primarily by the shoulder straps, with limited support from the belt or waistband, the center of gravity of the pack tends to be displaced downwardly and outwardly. This further acts to limit the load carrying capacity and reduce the comfort of the user. In a number of situations, the mobility of the user, and control of backpack position and load movement are of primary importance, such as with the skier and the climber. In both instances, positive control over the load, and maintenance of the sense of balance of the user, without restriction of movement or the imposition of stressful loads, are of greatest importance.
An even more critical example of this type of demanding situation is the backpack for a scuba diver. The pack should support one or two air cylinders, present low resistance to the water as the diver moves, and therefore have a low profile, while not acting to restrict the diving and swimming movements of the user. At the same time, conventional pockets for gear and holders for accessories should be included. Even more, it is desirable to incorporate a "buoyancy compensation" feature. This type of pack has an inflatable bladder or internal chamber, and can be expanded by oral inflation or by using air from the tank. Thus it provides a means for precisely compensating for the diver's weight belt and other equipment at a given depth, so as to minimize the work involved in maintaining a given location. Examples of this type of system are found in the U.S. Pat. Nos. to Greenwood, 3,436,777, Deeds, 4,054,132, Faulconer et al., 4,810,134, Walters, 4,952,095, Walters, 4,016,616, Faulconer et al., 4,561,853, Wright III, 4,137,585, Courtney, 4,779,554, and UK specification No. GB 2197 627A.
Though the earlier systems were bulky, the state of the art has improved considerably, and the present buoyancy compensated (or BC) packs have different combinations of adjustable shoulder straps, flexible or non-stretching waist straps, rigid and semi-rigid tank holders, and different arrangements for the buoyancy compartments and for storage and utility pockets. None have the desirable combination of features that are now sought, including particularly allowing the freedom of motion to the diver, especially when the bladder is inflated. Further they do not provide firm yet non-restraining retention of the tank in a low profile configuration, easy adjustment, and low cost construction. For example, U.S. Pat. Nos. 4,009,583, 4,016,616, 4,137,585 and 4,779,554 all have rigid tank holders and backpacks, while U.S. Pat. No. 4,009,583 also incorporates a semi-rigid air container system with a rigid cover. In U.S. Pat. No. 4,952,095 the backpack is flexible, with an interior liquid, and the container made of a flexible material, while the tank holder is rigid. In this example the waist straps are flexible neoprene, foam rubber, or rigid nylon webbing. In U.S. Pat. No. 4,810,134, the tank holder is rigid, the shoulder straps are non-extendable, and are adjustable only at D-rings or locked buckles. Flexible waistband straps of neoprene foam rubber are utilized, in accordance with U.S. Pat. No. 4,694,772, which describes a buoyancy compensation feature and is said to be automatic. None of these teachings provides a suitable combination of all the features that are desired.